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Dorsal spines (total): 0-0; Dorsal soft rays (total): 15-16; Anal spines: 0-0; Anal soft rays: 17-18. Diagnosis: Nothobranchius prognathus differs from all other species of the Nothobranchius melanospilus complex in possessing lower jaw anteriorly projecting beyond upper jaw vs. not projecting; pelvic fins medially united in males vs. bases just in contact, but not united; and presence of three longitudinal series of scales on frontal region vs. two (Ref. 119668). It is also distinguished from all other species of the N. melanospilus complex by the combination of the following morphological character states: dorsal-fin origin anterior to anal-fin origin in both sexes vs. posterior in N. melanospilus; anterior supraorbital series of neuromasts divided in two sections vs. arranged in a single continuous row in N. melanospilus; mandibular neuromasts 14-16 vs. 17-21 in N. melanospilus; in females, few dark spots on anterior part of flank vs. dots absent on anterior part in N. melanospilus; body depth 32.7-35.5% of standard length in males, 32.1-33.4% of standard length in females vs. 27.5-32.2% and 27.1-30.9% of standard length in N. melanospilus and 28.7-30.9% and 25.8% of standard length in N. kwalensis; dorsal-fin base length 27.9-29.9% of standard length in males, 23.5-25.0% of standard length in females vs. 24.6-27.9% and 19.9-23.4% of standard length in N. melanospilus and 24.1-27.3% and 2.9% of standard length in N. kwalensis; head depth 90.4-99.2% of head length in males, 85-6-90.3% of head length in females vs. 78.0-87.8% and 74.6-80.7% of head length in N. melanospilus and 79.0-82.9% and 69.5% of head length in N. kwalensis; eye diameter 20.9-25.9% of head length in males, 21.1-24.4% of head length in females vs. 26.8-28.4% and 27.1% in N. kwalensis (Ref. 119668).
Description: Dorsal and ventral profiles slightly convex from snout to posterior end of dorsal and anal-fin bases, about straight on caudal peduncle; body moderately deep, compressed; greatest body depth at vertical just in front of pelvic-fin base (Ref. 119668). Jaws short, snout weakly pointed in lateral view; mouth superior, lower jaw anteriorly projecting beyond upper jaw; jaw teeth canine, numerous, irregularly arranged, outer teeth greater than internal teeth (Ref. 119668). Gill-rakers of first branchial arch 4+15; six branchiostegal rays (Ref. 119668). Dorsal and anal fins broad in males, extremity rounded, with short filamentous rays along distal margin, dorsal fin longer than anal fin; in females, dorsal fin rounded, anal fin sub-triangular and slightly longer than dorsal fin; caudal fin subtruncate; pectoral fin rounded, posterior extremity between pelvic-fin base and anus; pelvic fin small, tip reaching between urogenital papilla and base of second anal fin rays in males, reaching anus in females; pelvic-fin bases united in males, separated by minute interspace in females; dorsal-fin origin on vertical between base of first and second anal-fin rays in males, just anterior to anal-fin origin in females; dorsal-fin rays 15-16; anal-fin rays 17-18; caudal-fin rays 29; pectoral-fin rays 20; pelvic-fin rays 6; in males, minute papillate contact organs on first and second pectoral-fin rays and distal portion of middle dorsal-fin rays, and rows of well-developed papillate contact organs along two thirds of most rays of anal fin (Ref. 119668). Scales small, cycloid; body and head entirely scaled, except ventral surface of head; minute filamentous contact organs along posterior margin of scales on middle portion of flank and latero-ventral portion of head in males; body squamation extending over anterior 30% of caudal-fin base; no scales on dorsal and anal-fin bases; frontal squamation irregularly arranged in three longitudinal rows; longitudinal series of scales 29-30; transversse series of scales 10-12; scale rows around caudal peduncle 16 (Ref. 119668). Anterior supraorbital series of neuromasts arranged in two separate sections, each placed in shallow depression, the anterior section with two neuromasts, the posterior one with three; sometimes minute neuromast between depressions; posterior supraorbital series with four neuromasts placed in shallow depression; infraorbital series with 18-22 neuromasts, pre-opercular series 15-16, mandibular 14-16; one neuromast per scale of lateral line (Ref. 119668).
Colouration: Colouration in alcohol of males: trunk and head light brown, slightly darker on dorsum and lighter on venter; branchiostegal membrane dark grey; dorsal and anal fins hyaline; pale transverse series of grey spots on dorsal fin; caudal fin yellowish hyaline; sometimes narrow black line along whole fin margin, slightly broader on posterior dorsal corner; pectoral fin hyaline, pelvic fin greyish hyaline with black tip (Ref. 119668). Colouration in alcohol of females: trunk and head light brown, slightly darker on dorsum and lighter on venter; small dark brown to black dots irregularly arranged on whole flank, often coalesced to form inverted V or Y-shaped spots, more concentrated on posterior half of flank; few similar dots on head side; unpaired fins hyaline; small dark grey dots arranged in five transverse rows on dorsal fin, and arranged in two irregular rows on basal portion of anal and caudal fins; paired fins hyaline (Ref. 119668). |
